The investigators will check the feasibility of using early molecular response for making treatment decisions. Patients diagnosed with chronic myeloid leukemia will commence imatinib treatment. After 3 months of treatment their response will be assessed. If molecular response would be less the 10% (BCR-ABL1/ABL ISI >10%)imatinib therapy will be stopped and patients will start a different TKI (as nilotinib, dasatinib). The investigators will follow on lab and clinical outcomes.